Wrote a Clite parser– in Prolog!
parser.pl:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 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parse('sourcefile','destfile'). to output parse to specified file.% Starting call, Output to terminal.parse(FileIn) :-runparser(FileIn, user_output).% Starting call, Output to file.parse(FileIn, FileOut) :-open(FileOut, write, OutFileStream),runparser(FileIn, OutFileStream),close(OutFileStream).% Main Routinerunparser(FileIn, OutStream) :-open(FileIn, read, InFileStream),build_token_list(InFileStream, TokenList),close(InFileStream),build_parse_tree(TokenList, ParseTree),print_parse_tree(ParseTree, OutStream).%----- Token List Functions-----%% Converts the token stream into a list of pairs of format (Token, Token_Type).build_token_list(InStream, _) :-at_end_of_stream(InStream), !.build_token_list(InStream, TokenList) :-+ at_end_of_stream(InStream),readToken(InStream, Token),readToken(InStream, Token_Type),build_token_list(InStream, NextToken),TokenList = [(Token, Token_Type) | NextToken].% Grabs the next ASCII code out of the stream and builds into a Word, then unifies it back into an atom.readToken(InStream, Word):-get_code(InStream, Char),buildtoken(Char, Chars, InStream),atom_codes(Word, Chars).% The following ASCII codes indicate the end of a word.buildtoken(10,[],_):- !. % newlinebuildtoken(9,[],_):- !. % tabbuildtoken(32,[],_):- !. % spacebuildtoken(-1,[],_):- !. % end of streambuildtoken(end_of_file,[],_):- !. % eof% Grab chars and append them to our list until we hit the end of a word, as defined above.buildtoken(Char,[Char|Rest],InStream):-get_code(InStream,NextChar),buildtoken(NextChar,Rest,InStream).%----- Token List Functions-----%% Initial call to the DCG functionalitybuild_parse_tree(Tokens, ParseTree) :-s_program(ParseTree, Tokens, []).%----- DCG Definitions for Clite-----%% Used < > in place of EBNF metabrackets in the comments,% and _{_ _}_ to designate EBNF metabraces.% Had to make 4 different definitions for Program to allow for programs with no declarations and/or statements.% This is a bit of a workaround to keep the parse tree tidy.% Program -> int main ( ) { Declarations Statements }s_program(program(IntTok, MainTok, LPTok, RPTok, LCBTok, declarations(Declarations), statements(Statements), RCBTok)) -->[(IntTok, 'INT')],[(MainTok, 'MAIN')],[(LPTok, 'LPAREN')],[(RPTok, 'RPAREN')],[(LCBTok, 'LBRACE')],s_declarations(Declarations),s_statements(Statements),[(RCBTok, 'RBRACE')], !.% Program -> int main ( ) { Declarations }s_program(program(IntTok, MainTok, LPTok, RPTok, LCBTok, declarations(Declarations), RCBTok)) -->[(IntTok, 'INT')],[(MainTok, 'MAIN')],[(LPTok, 'LPAREN')],[(RPTok, 'RPAREN')],[(LCBTok, 'LBRACE')],s_declarations(Declarations),[(RCBTok, 'RBRACE')], !.% Program -> int main ( ) { Statements }s_program(program(IntTok, MainTok, LPTok, RPTok, LCBTok, statements(Statements), RCBTok)) -->[(IntTok, 'INT')],[(MainTok, 'MAIN')],[(LPTok, 'LPAREN')],[(RPTok, 'RPAREN')],[(LCBTok, 'LBRACE')],s_statements(Statements),[(RCBTok, 'RBRACE')], !.% Program -> int main ( ) { }s_program(program(IntTok, MainTok, LPTok, RPTok, LCBTok, RCBTok)) -->[(IntTok, 'INT')],[(MainTok, 'MAIN')],[(LPTok, 'LPAREN')],[(RPTok, 'RPAREN')],[(LCBTok, 'LBRACE')],[(RCBTok, 'RBRACE')], !.% Declarations -> _{_ Declaration _}_s_declarations(Decl) --> s_declaration(Decl).s_declarations((Decl, MoreDecls)) -->s_declaration(Decl),s_declarations(MoreDecls).s_declarations(_) --> [].% Declaration -> Type Identifier <[Integer]>_{_, Identifier <[Integer]>_}_;s_declaration(declaration(Type, Ident, SemiTok)) -->s_type(Type),s_identifier(Ident),[(SemiTok, 'SEMICOL')].s_declaration(declaration(Type, Ident, LBTok, Int, RBTok, SemiTok)) -->s_type(Type),s_identifier(Ident),[(LBTok, 'LBRACK')],s_intvalue(Int),[(RBTok, 'RBRACK')],[(SemiTok, 'SEMICOL')].s_declaration(declaration(Type, Ident, CommaTok, NextDecl)) -->s_type(Type),s_identifier(Ident),[(CommaTok, 'COMMA')],s_declaration_commaseparatedlist(NextDecl).s_declaration(declaration(Type, Ident, LBTok, Int, RBTok, CommaTok, NextDecl)) -->s_type(Type),s_identifier(Ident),[(LBTok, 'LBRACK')],s_intvalue(Int),[(RBTok, 'RBRACK')],[(CommaTok, 'COMMA')],s_declaration_commaseparatedlist(NextDecl).s_declaration_commaseparatedlist(comma(Ident, SemiTok)) -->s_identifier(Ident),[(SemiTok, 'SEMICOL')].s_declaration_commaseparatedlist(comma(Ident, LBTok, Int, RBTok, SemiTok)) -->s_identifier(Ident),[(LBTok, 'LBRACK')],s_intvalue(Int),[(RBTok, 'RBRACK')],[(SemiTok, 'SEMICOL')].s_declaration_commaseparatedlist(comma(Ident, CommaTok, NextDecl)) -->s_identifier(Ident),[(CommaTok, 'COMMA')],s_declaration_commaseparatedlist(NextDecl).s_declaration_commaseparatedlist(comma(Ident, LBTok, Int, RBTok, CommaTok, NextDecl)) -->s_identifier(Ident),[(LBTok, 'LBRACK')],s_intvalue(Int),[(RBTok, 'RBRACK')],[(CommaTok, 'COMMA')],s_declaration_commaseparatedlist(NextDecl).s_type(type(TypeTok)) -->[(TypeTok, 'INT')] ;[(TypeTok, 'BOOL')] ;[(TypeTok, 'FLOAT')] ;[(TypeTok, 'CHAR')].% Statements -> _{_Statement_}_s_statements(Statement) --> s_statement(Statement).s_statements((Statement, MoreStatements)) --> s_statement(Statement), s_statements(MoreStatements).s_statements(_) --> [].% Statement -> ; | Block | Assignment | IfStatement | WhileStatements_statement(statement(SemiColTok)) --> [(SemiColTok, 'SEMICOL')].s_statement(statement(Block)) --> s_block(Block).s_statement(statement(Assign)) --> s_assignment(Assign).s_statement(statement(IfStatement)) --> s_if_statement(IfStatement).s_statement(statement(WhileStatement)) --> s_while_statement(WhileStatement).% Block -> { Statements }s_block(block(LCBTok, Statements, RCBTok)) -->[(LCBTok, 'LBRACE')],s_statements(Statements),[(RCBTok, 'RBRACE')].% Assignment -> Identifier <[Expression]> = Expression;s_assignment(assignment(Target, AssignOpTok, Source, SemiTok)) -->s_identifier(Target),[(AssignOpTok, 'ASSIGN')],s_expression(Source),[(SemiTok, 'SEMICOL')].s_assignment(assignment(Target, LBTok, Expr, RBTok, AssignOpTok, Source, SemiTok)) -->s_identifier(Target),[(LBTok, 'LBRACK')],s_expression(Expr),[(RBTok, 'RBRACK')],[(AssignOpTok, 'ASSIGN')],s_expression(Source),[(SemiTok, 'SEMICOL')].% IfStatement -> if ( Expression ) Statements_if_statement(if_statement(IfTok, LPTok, Test, RPTok, ThenBlock)) -->[(IfTok, 'IF')],[(LPTok, 'LPAREN')],s_expression(Test),[(RPTok, 'RPAREN')],s_statement(ThenBlock).s_if_statement(if_statement(IfTok, LPTok, Test, RPTok, ThenBlock, ElseTok, ElseBlock)) -->[(IfTok, 'IF')],[(LPTok, 'LPAREN')],s_expression(Test),[(RPTok, 'RPAREN')],s_statement(ThenBlock),[(ElseTok, 'ELSE')],s_statement(ElseBlock).% WhileStatement -> while ( Expression ) Statements_while_statement(while_statement(WhileTok, LPTok, Test, RPTok, Statement)) -->[(WhileTok, 'WHILE')],[(LPTok, 'LPAREN')],s_expression(Test),[(RPTok, 'RPAREN')],s_statement(Statement).% Expression -> Conjunction _{_|| Conjunction _}_s_expression(expression(Expr)) --> s_conjunction(Expr).s_expression(expression(Expr1, OrOpTok, Expr2)) -->s_conjunction(Expr1),[(OrOpTok, 'OR_OP')],s_expression(Expr2).% Conjunction -> Equality _{_&& Equality _}_s_conjunction(conjunction(Conj)) --> s_equality(Conj).s_conjunction(conjunction(Conj1, AndOpTok, Conj2)) -->s_equality(Conj1),[(AndOpTok, 'AND_OP')],s_conjunction(Conj2).% Equality -> Relations_equality(equality(Eq)) --> s_relation(Eq).s_equality(equality(Eq1, EqOp, Eq2)) -->s_relation(Eq1),s_equ_op(EqOp),s_relation(Eq2).% EquOp -> == | !=s_equ_op(equ_op(EQOp)) -->[(EQOp, 'EQ_OP')] ;[(EQOp, 'NE_OP')].% Relation -> Additions_relation(relation(Rel)) --> s_addition(Rel).s_relation(relation(Rel1, RO, Rel2)) --> s_addition(Rel1), s_rel_op(RO), s_addition(Rel2).% RelOp -> < | <= | > | >=s_rel_op(rel_op(ROp)) -->[(ROp, 'LT_OP')] ;[(ROp, 'LE_OP')] ;[(ROp, 'GT_OP')] ;[(ROp, 'GE_OP')].% Addition -> Term _{_AddOp Term_}_s_addition(addition(Add)) --> s_term(Add).s_addition(addition(Add1, AOp, Add2)) -->s_term(Add1),s_add_op(AOp),s_addition(Add2).% AddOp -> + | -s_add_op(add_op(AOp)) -->[(AOp, 'ADD_OP')] ;[(AOp, 'SUB_OP')].% Term -> Factor _{_MulOp Factor_}_s_term(term(Term)) --> s_factor(Term).s_term(term(Term1, MOp, Term2)) -->s_factor(Term1),s_mul_op(MOp),s_term(Term2).% MulOp -> * | / | %s_mul_op(mul_op(MOp)) -->[(MOp, 'MUL_OP')] ;[(MOp, 'DIV_OP')] ;[(MOp, 'MOD_OP')].% Factor -> Primarys_factor(factor(Factor)) --> s_primary(Factor).s_factor(factor(UOp, Factor)) --> s_unary_op(UOp), s_primary(Factor).% UnaryOp -> - | !s_unary_op(unary_op(UOp)) -->[(UOp, 'SUB_OP')] ;[(UOp, 'NOT_OP')].% Primary -> Identifier <[Expression]> | Literal | ( Expression ) | Type ( Expression )s_primary(primary(Prim)) --> s_identifier(Prim).s_primary(primary(Id, LBTok, Expr, RBTok)) -->s_identifier(Id) ;[(LBTok, 'LBRACK')],s_expression(Expr),[(RBTok, 'RBRACK')].s_primary(primary(Prim)) --> s_literal(Prim).s_primary(primary(LPTok, Expr, RPTok)) -->[(LPTok, 'LPAREN')],s_expression(Expr),[(RPTok, 'RPAREN')].s_primary(primary(Type, LPTok, Expr, RPTok)) -->s_type(type(Type)),[(LPTok, 'LPAREN')],s_expression(Expr),[(RPTok, 'RPAREN')].% Identifier -> Letter _{_ Letter | Digit _}_% Our lexer already handles this.s_identifier(identifier(Ident)) --> [(Ident, 'IDENT')].% Literal -> Integer | Boolean | Float | Char% Our lexer handled these already.s_literal(literal(Val)) -->s_intvalue(Val) ;s_floatvalue(Val) ;s_boolvalue(Val) ;s_charvalue(Val).s_intvalue(integer(Val)) --> [(Val, 'INTEGER')].s_boolvalue(boolean(Val)) --> [(Val, 'BOOLVAL')].s_floatvalue(float(Val)) --> [(Val, 'FLOAT')].s_charvalue(char(Val)) --> [(Val, 'CHAR_LIT')].%----- Pretty Printing Functions-----%% These handle converting our parse tree, currently a messy Prolog ground term,% into a nicely-formatted and indented rendition.% Initial call handler.print_parse_tree(Term_ParseTree, OutStream) :-write_to_codes(Term_ParseTree, Codes_ParseTree),print_indented(Codes_ParseTree, 0, OutStream).% Main printing routine. Clears punctuation and adjusts indentation,% then prints a word and recursively calls itself.print_indented([],_,_).print_indented(Codes, Level, OutStream) :-handle_punctuation(Codes, Rest, Level, NewLevel, OutStream),print_word(Rest, Tail, NewLevel, OutStream),print_indented(Tail, NewLevel, OutStream), !.% handle_punctuation handles adjusting indentation and clearing punctuation from the parse tree.handle_punctuation([], [], _, _).handle_punctuation([40|Codes], Rest, Level, NewLevel, OutStream) :- % Case (NewLevel is Level + 1,handle_punctuation(Codes, Rest, NewLevel, _, OutStream), !.handle_punctuation([123|Codes], Rest, Level, FinalLevel, OutStream) :- % Case {NewLevel is Level + 1,handle_punctuation(Codes, Rest, NewLevel, FinalLevel, OutStream), !.handle_punctuation([41|Codes], Rest, Level, FinalLevel, OutStream) :- % Case )NewLevel is Level - 1,handle_punctuation(Codes, Rest, NewLevel, FinalLevel, OutStream), !.handle_punctuation([125|Codes], Rest, Level, FinalLevel, OutStream) :- % Case }NewLevel is Level - 1,handle_punctuation(Codes, Rest, NewLevel, FinalLevel, OutStream), !.handle_punctuation([44|Codes], Rest, Level, FinalLevel, OutStream) :- % Case ,handle_punctuation(Codes, Rest, Level, FinalLevel, OutStream), !.handle_punctuation([32|Codes], Rest, Level, FinalLevel, OutStream) :- % Case ' 'handle_punctuation(Codes, Rest, Level, FinalLevel, OutStream), !.handle_punctuation(Codes, Codes, Level, Level, _). % No punctuation found.% print_word handles indentation, calls the word-fetcher, and outputs a newline.print_word([], Rest, _, _) :- Rest = [].print_word(Codes, Rest, Level, OutStream) :-NumTabs is Level * 2,tab(OutStream, NumTabs),get_word(Codes, Rest, Level, OutStream),put_char(OutStream, 'n'), !.% get_word builds a string until the specified punctuation is found.get_word([], _, _, _). % End of wordget_word([40|Codes], [40|Codes], _, _) :- !. % (get_word([41|Codes], [41|Codes], _, _) :- !. % )get_word([44|Codes], [44|Codes], _, _) :- !. % ,get_word([32|Codes], [32|Codes], _, _) :- !. % ' 'get_word([123|Codes], [123|Codes], _, _) :- !. % {get_word([125|Codes], [125|Codes], _, _) :- !. % }get_word([Char|Codes], Rest, Level, OutStream) :-put_code(OutStream, Char),get_word(Codes, Rest, Level, OutStream). |
